To cut a nice gemstone from tourmaline that has closed ends (very little if any light is transmitted down the principle, c, axis.) restricts your options as a cutter. The choice of the emerald cut is essential for minimizing the impact of the dark ends caused by their closed nature. To minimize the amount of incursion of the closed ends into the colorful a/b axis that you hope to accentuate, the “normal” angels (forty degree angles next to the keel) used on the sides and ends of an open emerald cut are recommend to be increased to the seventy degree range for the row of facets closest to the girdle. The angles are also increased for the corners. Now I have made the effort outlined above on many of my gemstones with closed ends, but not all.
I have developed personal preferences over the years when it comes to cutting tourmaline. I have found that traditional cuts are both well suited for my technology and my aesthetics. So I have come to use only a limited number of more modern cuts to enhance the beauty of appropriate tourmaline. In the case of tourmaline with closed/dark ends, I have found that I prefer the flash and shape (normal emerald cuts have their girdle corners cut down less than steep ended emerald cuts) of an emerald cut that has the same angles as a normally cut emerald cut. Yes, this does increase the amount of darkness in the ends of the emerald cut, but on the posted gemstone and others, with a large ratio between their length and width, it matters little.
This beautiful large green emerald cut is a tower of green power. The bands of beautiful green seem to go on forever, but are seated in cups of flash from the reflection of the a/b axis off the ends when it is moved. The ends are dead/dark when stationary or moved without tilting, but the gemstone has a large ratio of length to width that lessens this effect without demanding steep ends. So a cutter’s choice has been made and the wonderful medium grass green and purity of this impressive tourmaline shines brightly in the collection. It weighs 12.30 carats.